The galvanic cell has become a primary power source for many portable electronic devices such as tape recorders, portable telephones, lanterns, radios, hearing aids, watches, calculators and the like. In order to maintain the overall electronic devices as compact as possible, the electronic devices are usually designed with cavities to accommodate batteries as their power source. The cavities are usually made so that a battery can be snugly positioned therein, thus making electronic contact with appropriate terminals within the device. To accommodate the electronic component manufacturers, the battery industry has adapted several conventional size cells which the manufacturers can rely upon in designing their devices which require portable power sources. Due to the large number of battery-powered devices on the market, there has been a demand for increased power output capacities of standard size cells. Accordingly, various cell constructions have been employed so as to provide a sufficient output capacity to operate various devices. A problem has been encountered, however, when the cell is short circuited or discharged under abuse conditions which could produce a large current flow that could result in a high temperature rise in the cell. This elevated temperature rise could also produce excessive pressure build-up which independently or together could provide an environment within the cell inductive for an uncontrollable explosion to occur or rupture of the cell's housings.
Various preventive means have been employed in or on a cell to prevent excessive current flow such as would result from a short circuit. Many of these means require mechanical and/or electrical components to be assembled in or on the cell to break the current once the current exceed a predetermined level. These means have the disadvantage of adding cost to the production of the cell and in some instances occupy space that could be used for the active materials of the cell.
U.S. Pat. No. 4,188,460 discloses a battery employing an internal battery fuse which comprises a portion of a current collector that is thermally shielded so that excessive build-up of heat resulting from a short circuit is concentrated in said portion and which heat fuses the shielded portion and interrupts the circuit prior to excessive internal pressure conditions.
It is an object of the present invention to provide a battery terminal fuse that is cost effective to make and that occupies only a small space within the battery.
It is another object of the present invention to provide a novel safety means for interrupting or breaking the circuit once the current exceeds a predetermined value.
It is another object of the present invention to provide a single conductive tab that is not required to be thermally shielded and which will function to interrupt or break the circuit of the cell once the current exceeds a predetermined value.
The foregoing and additional objects will become fully apparent from the following description.